B.5 P-CSCF Restoration

29.2133GPPPolicy and charging control signalling flows and Quality of Service (QoS) parameter mappingRelease 17TS

This clause is applicable if P-CSCF Restoration is to be performed.

Figure B.5.1: P-CSCF Restoration

1. The P-CSCF sends an AAR command to PCRF to initiate a P-CSCF Restoration procedure, as defined in the 3GPP TS 23.380 [35]. The AAR command contains a Rx-Request-Type AVP with value set to PCSCF_RESTORATION and can contain the IP address of the UE within Framed-IP-Address AVP (if available) or the Framed-Ipv6-Prefix AVP (if available), IMSI (if available) within the Subscription-Id AVP, the IMS APN (if available) within the Called-Station-Id AVP and/or the IP address domain (if available) within the IP-Domain-Id AVP.

For the non-roaming case and the home routed case, the H-PCRF receives the AAR command, i.e. step 1 is executed.

1a. For the roaming case with visited access, when the P-CSCF is located in the VPLMN, step 1 is executed with the exception that the V-PCRF receives the AAR command and responds with the AAA command

2. When receiving the AAR command for P-CSCF Restoration from the P-CSCF, the PCRF acknowledges the AAR by sending an AAA command to the P-CSCF.

For the non-roaming case and the home routed case, the H-PCRF sends an AAA command to the P-CSCF, i.e. step 2 is executed.

2a. For the roaming case with visited access, when the P-CSCF is located in the VPLMN, step 2 is executed with the exception that the V-PCRF sends an AAA command to the P-CSCF.

For the roaming case with local breakout when the P-CSCF is located in the HPLMN, when the H-PCRF receives the AAR command from the P-CSCF, the H-PCRF sends an RAR command to the V-PCRF, i.e. step 1b is executed.

3. When receiving the AAR command for P-CSCF Restoration, the PCRF finds the corresponding IP-CAN session according to the received information within the AAR command, and sends an RAR command for the corresponding IP-CAN session (IMS PDN connection) to the PCEF for P-CSCF Restoration. The RAR contains a PCSCF-Restoration-Indication AVP with value set to PCSCF_RESTORATION.

For the non-roaming case and the home routed case, when receiving the AAR command from the P-CSCF, the H-PCRF sends the RAR command to the PCEF, i.e. step 3 is executed.

3a, For the roaming case with visited access, when the P-CSCF is located in the VPLMN, step 3 is executed with the exception that when receiving the AAR command from the P-CSCF, the V-PCRF sends the RAR command to the PCEF.

For the roaming case with local breakout when the P-CSCF is located in the HPLMN, when receiving the RAR command from the H-PCRF, the V-PCRF sends an RAR command to the PCEF, i.e. step 2a is executed.

4. When receiving the RAR command for P-CSCF Restoration, the PCEF acknowledges the RAR by sending an RAA command to the PCRF and performs the subsequent P-CSCF Restoration procedure as specified in 3GPP TS 23.380 [35].

NOTE 1: If the IMS PDN disconnection is performed for P-CSCF Restoration, the PCEF sends a CCR command to the PCRF to terminate the corresponding Gx session.

For the non-roaming case and the home routed case, when receiving the RAR command from the H-PCRF, the PCEF acknowledges this message by sending an RAA command to the H-PCRF, i.e. step 4 is executed.

4a. For the roaming case with visited access, when the P-CSCF is located in the VPLMN, step 4 is executed with the exception that when receiving the RAR command from the V-PCRF, the PCEF acknowledges this message by sending an RAA command to the V-PCRF.

NOTE 2: This P-CSCF Restoration procedure is applicable to the cases that both the P-CSCF and the PCEF are located in the same PLMN.